Sem inspection and analysis of patterned photoresist features

ABSTRACT

A process for improving the accuracy of critical dimension measurements of features patterned on a photoresist layer using a scanning electron microscope (SEM) is disclosed herein. The process includes providing an electron beam to the photoresist layer and transforming the surface of the photoresist layer before the SEM inspection. The surface of the photoresist layer is transformed to trap the outgassing volatile species and dissipates built up charge in the photoresist layer, resulting in SEM images without poor image contrast.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is related to U.S. Application Ser. No.______ (Atty. Dkt. No. 39153/403 (F0942)) by Shields et al., entitled“Process for Forming Sub-Lithographic Photoresist Features byModification of the Photoresist Surface;” U.S. Application Ser. No.______ (Atty. Dkt. No. 39153/404 (F0943)) by Okoroanyanwu et al.,entitled “Process for Preventing Deformation of Patterned PhotoresistFeatures by Electron Beam Stabilization;” U.S. Application Ser. No.______ (Atty. Dkt. No. 39153/406 (F1061)) by Okoroanyanwu et al.,entitled “Process for Reducing the Critical Dimensions of IntegratedCircuit Device Features;” U.S. Application Ser. No. ______ (Atty. Dkt.No. 39153/298 (F0785)) by Gabriel et al., entitled “SelectivePhotoresist Hardening to Facilitate Lateral Trimming;” and U.S.Application Ser. No. ______ (Atty. Dkt. No. 39153/310 (F0797)) byGabriel et al., entitled “Process for Improving the Etch Stability ofUltra-Thin Photoresist,” all filed on an even date herewith and assignedto the Assignee of the present application.

FIELD OF THE INVENTION

[0002] The present invention relates generally to integrated circuits(ICs). More particularly, the present application relates to a methodand apparatus for improved scanning electron microscope (SEM) inspectionand analysis of patterned photoresist features utilized to fabricateICs.

BACKGROUND OF THE INVENTION

[0003] During integrated circuit (IC) fabrication, various surfacesinvolved therein are inspected and analyzed for a variety of reasons.For example, the dimensions of features provided on a given surface maybe measured and/or their alignment with respect to other features may beanalyzed. Features provided on a given surface may be inspected foruniformity, integrity and/or defects. A semiconductor substrate,photoresist feature, or a layer above the semiconductor substrate can beinspected.

[0004] The semiconductor substrate or a layer above the semiconductorsubstrate, collectively, a semiconductor wafer, may be inspected todetermine whether further processing should continue, whether the wafershould be discarded, or whether an appropriate corrective measure shouldbe taken before further processing of the wafer continues. In thismanner, the likelihood of defects occurring during the IC fabricationprocess can be decreased or eliminated.

[0005] Various techniques can be utilized to inspect and analyze thewafer. Optical microscopes, scanning electron microscopes (SEMs), orlaser-based systems may be utilized for inspection and measurementtasks. Some of the tasks require human involvement and others are fullyautomated so that human involvement is unnecessary.

[0006] Layers or surfaces which are present on the wafer only during theIC fabrication process (i.e., layers or surfaces which do not comprisethe end product IC) are also commonly inspected. For example, layers ofphotoresist material can be inspected following development(after-develop-inspection or “ADI”) to ensure that the pattern transferprocess has been performed correctly and/or that the pattern is withinspecified tolerances. From such inspection, mistakes or unacceptableprocess variations associated with the layer of photoresist material canbe identified and corrected since the layer of photoresist material hasnot yet been utilized to produce any physical changes to the waferitself, such as, by doping, etching, etc. Defective layers ofphotoresist material can be corrected by stripping and reapplying a newlayer of photoresist material on the wafer.

[0007] Critical dimensions of patterned features on a layer ofphotoresist material are commonly measured using an SEM inspection andanalysis tool. This measurement task involves obtaining SEM images ofthe patterned features. The SEM inspection and analysis tool obtains SEMimages of a given sample using an inspection electron beam, theinspection electron beam characterized by a low beam current (on theorder of pA) and an accelerating voltage of approximately 300-1500 V.The sample is rapidly scanned by the inspection electron beam so as toobtain imaging data but not long enough to intentionally affect thesample.

[0008] The SEM inspection and analysis tool includes an electron gun,one or more lens assemblies, and photomultiplier detectors, all within avacuum environment at approximately 10⁻⁷ Torr. Electrons emitted fromthe electron gun, i.e., the inspection electron beam, are focused by thelens assemblies to form primary electrons that impinge on a sample to beimaged (e.g., the patterned layer of photoresist material). Theinteraction of the impinging primary electrons with the surface of thesample causes secondary electrons to be emitted from the sample. Thesecondary electrons are generated from the top portion of the sample,within a depth of approximately 50-60 Å from the top surface. Thesesecondary electrons are collected by the photomultiplier detectors andcomprise the imaging data from which SEM images are generated.

[0009] However, when the photoresist material is an organic-basedphotoresist material, SEM images of features patterned thereon aresusceptible to poor image contrast, and this in turn may lead toerroneous critical dimension measurements. SEM images with degradedimage contrast are caused by undesirable interaction of the primaryelectrons with the sample (e.g., the organic-based photoresistmaterial). Instead of merely causing secondary electrons to be emittedfrom the organic-based photoresist material, the primary electrons mayalso cause volatile organic species to be emitted or outgassed from theorganic-based photoresist material (i.e., the outgassing problem). Thesevolatile organic species interact with and scatter the secondaryelectrons such that the secondary electrons that are collected by thephotomultiplier detectors are distorted imaging data representative ofthe patterned features on the photoresist material. Consequently, SEMimages generated therefrom are less than ideal, such as, suffering fromdegraded image contrast.

[0010] Additionally, organic-based photoresist materials have a tendencyto build up charge and/or heat from the impinging primary electrons(i.e., the charging and heating problems). Organic-based photoresistmaterials exhibit insulative properties and can build up charge and/orheat from the beam current of the primary electrons. Because theconstituents comprising the organic-based photoresist material havevarying insulative properties with respect to each other, charge and/orheat dissipation is also non-uniform and/or insignificant. Whenexcessive charge and/or heat builds up within the material, structuralor physical changes can occur such that patterned features may becomepermanently distorted and damaged. Hence, not only are the SEM imagesinaccurate but subsequent pattern transfer to underlying layers of thewafer is also adversely impacted. As features are lithographicallypatterned at ever decreasing dimensions, the outgassing, charging,and/or heating problems associated with SEM imaging of organic-basedphotoresist surfaces are becoming progressively worse.

[0011] Thus, there is a need for improved SEM inspection and analysis ofpatterned features on a layer of photoresist material. There is afurther need for a process for reducing charging and/or heating problemsassociated with SEM imaging of organic-based photoresist materials.There is still a further need for a process for reducing undesirableoutgassing problems associated with SEM imaging of organic-basedphotoresist materials.

BRIEF SUMMARY OF THE INVENTION

[0012] One exemplary embodiment relates to a method of inspecting asurface associated with manufacture of an integrated circuit. The methodincludes providing an electron beam to the surface, and transforming atleast a portion of the surface. The method further includes inspectingthe surface using a scanning electron microscope (SEM). The transformingstep occurs before the inspecting step.

[0013] Another exemplary embodiment relates to a patterned photoresistlayer. The layer is configured to facilitate accurate critical dimensionmeasurements of features thereon using a scanning electron microscope(SEM). The layer includes a treated region and an untreated region. Thetreated region comprises a top surface and side surfaces surrounding theuntreated region. The treated region has at least one of a differentelectrical and material property relative to the untreated region.

[0014] Still another exemplary embodiment relates to a process forreducing the build up of at least one of charge, heat, and volatilespecies in a photoresist layer during scanning electron microscope (SEM)inspection. The process includes exposing the photoresist layer to aflood electron beam, and forming a shell in the photoresist layer inresponse to the flood electron beam. The photoresist layer includes atleast one patterned feature having a top surface, side surfaces, and anuntreated portion. The shell is comprised of the top surface and theside surfaces. The shell reduces the build up of at least one of charge,heat, and volatile species associated with at least one feature duringSEM inspection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The exemplary embodiments will become more fully understood fromthe following detailed description, taken in conjunction with theaccompanying drawings, wherein like reference numerals denote likeelements, in which:

[0016]FIG. 1 is a flow diagram showing a process for obtaining accuratecritical dimension measurements in accordance with an exemplaryembodiment;

[0017]FIG. 2 is a general schematic block diagram of a lithographicsystem for patterning a wafer in accordance with an exemplaryembodiment;

[0018]FIG. 3 is a cross-sectional view of the wafer illustrated in FIG.2, showing a developing step;

[0019]FIG. 4 is a cross-sectional view of the wafer illustrated in FIG.3, showing an electron beam exposure step; and

[0020]FIG. 5 is a scanning electron microscope (SEM) analysis andinspection tool in accordance with an exemplary embodiment.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0021] In one embodiment of the present invention, an advantageousprocess for obtaining accurate critical dimension (CD) measurements offeatures patterned on a photoresist layer during an integrated circuit(IC) fabrication is provided. An exemplary embodiment of the presentinvention will be described with respect to a flow diagram shown inFIG. 1. The flow diagram includes a patterning step 40, a developingstep 42, an electron beam exposure step 44, a scanning electronmicroscope (SEM) analysis and inspection step 46, and a criticaldimension measurements step 48.

[0022] Patterning step 40 is carried out using a lithography system 10,as shown in FIG. 2. Lithographic system 10 includes a chamber 12, alight source 14, a condenser lens assembly 16, a mask or a reticle 18,an objective lens assembly 20, and a stage 22. Lithographic system 10 isconfigured to transfer a pattern or image provided on mask or reticle 18to a wafer 24 positioned in lithography system 10. Lithographic system10 may be a lithographic camera or stepper unit. For example,lithographic system 10 may be a PAS 5500/900 series machine manufacturedby ASML, a microscan DUV system manufactured by Silicon Valley Group, oran XLS family microlithography system manufactured by IntegratedSolutions, Inc. of Korea.

[0023] Wafer 24 includes a substrate 26, a layer 28, and a photoresistlayer 30. Photoresist layer 30 is disposed over layer 28, and layer 28is disposed over substrate 26. Wafer 24 can be an entire integratedcircuit (IC) wafer or a part of an IC wafer. Wafer 24 can be a part ofan IC, such as, a memory, a processing unit, an input/output device,etc. Substrate 26 can be a semiconductor substrate, such as, silicon,gallium arsenide, germanium, or other substrate material. Substrate 26can include one or more layers of material and/or features, such aslines, interconnects, vias, doped regions, etc., and can further includedevices, such as, transistors, microactuators, microsensors, capacitors,resistors, diodes, etc.

[0024] Layer 28 can be an insulative layer, a conductive layer, abarrier layer, or other layer of material to be etched, doped, orlayered. In one embodiment, layer 28 can comprise one or more layers ofmaterials, such as, a polysilicon stack comprised of a plurality ofalternating layers of titanium silicide, tungsten silicide, cobaltsilicide materials, etc. In another embodiment, layer 28 is a hard masklayer, such as, a silicon nitride layer or a metal layer. The hard masklayer can serve as a patterned layer for processing substrate 26 or forprocessing a layer upon substrate 26. In yet another embodiment, layer28 is an anti-reflective coating (ARC). Substrate 26 and layer 28 arenot described in a limiting fashion, and can each comprise a conductive,semiconductive, or insulative material.

[0025] Photoresist layer 30 can comprise a variety of photoresistchemicals suitable for lithographic applications. Photoresist layer 30is selected to have photochemical reactions in response toelectromagnetic radiation emitted from light source 14. Materialscomprising photoresist layer 30 can include, among others, a matrixmaterial or resin, a sensitizer or inhibitor, and a solvent. Photoresistlayer 30 is preferably a chemically amplified, positive or negativetone, organic-based photoresist. Photoresist layer 30 may be, but is notlimited to, an acrylate-based polymer, an alicyclic-based polymer, or aphenolic-based polymer. For example, photoresist layer 30 may comprisePAR700 photoresist manufactured by Sumitomo Chemical Company.Photoresist layer 30 is deposited, for example, by spin-coating overlayer 28. Photoresist layer 30 is provided at a thickness of less than1.0 μm.

[0026] Chamber 12 of lithographic system 10 can be a vacuum or lowpressure chamber for use in ultraviolet (UV), vacuum ultraviolet (VUV),deep ultraviolet (DUV), extreme ultraviolet (EUV), x-ray, or other typesof lithography. Chamber 12 can contain any of numerous types ofatmospheres, such as, nitrogen, etc. Alternatively, chamber 12 can beconfigured to provide a variety of other patterning scheme.

[0027] Light source 14 provides light or electromagnetic radiationthrough condenser lens assembly 16, mask or reticle 18, and objectivelens assembly 20 to photoresist layer 30. Light source 14 is an excimerlaser, in one embodiment, having a wavelength of 365 nm, 248 nm, 193 nm,157 nm, or 126 nm, or a soft x-ray source having a wavelength at 13.4nm. Alternatively, light source 14 may be a variety of other lightsources capable of emitting radiation having a wavelength in theultraviolet (UV), vacuum ultraviolet (VUV), deep ultraviolet (DUV),extreme ultraviolet (EUV), x-ray or other wavelength range.

[0028] Assemblies 16 and 20 include lenses, mirrors, collimators, beamsplitters, and/or other optical components to suitably focus and directa pattern of radiation (i.e., radiation from light source 14 as modifiedby a pattern or image provided on mask or reticle 18) onto photoresistlayer 30. Stage 22 supports wafer 24 and can move wafer 24 relative toassembly 20.

[0029] Mask or reticle 18 is a binary mask in one embodiment. Mask orreticle 18 includes a translucent substrate 32 (e.g., glass or quartz)and an opaque or absorbing layer 34 (e.g., chromium or chromium oxide)thereof. Absorbing layer 34 provides a pattern or image associated witha desired circuit pattern, features, or devices to be projected ontophotoresist layer 30. Alternatively, mask or reticle 18 may be anattenuating phase shift mask, an alternating phase shift mask, or othertype of mask or reticle.

[0030] Utilizing lithographic system 10, the pattern or image on mask orreticle 18 is projected onto and patterned on photoresist layer 30 ofwafer 24. Next, in developing step 42, wafer 24 is exposed to adeveloper, as is well-known in the art, to develop the pattern onphotoresist layer 30. Referring to FIG. 3, a cross-sectional view of aportion of wafer 24 after developing step 42 is shown. The developedpattern includes features 50 and 51.

[0031] After photoresist layer 30 has been developed but before featuresthereon are transferred onto any of the underlying layers, such as layer28, electron beam exposure step 44 is performed. Wafer 24 may be removedfrom chamber 12 and placed within a different chamber and/or a differentenvironment which provides electron beam tools. Alternatively, chamber12 may be configured to include additional chambers and/or toolssuitable to perform step 44.

[0032] In FIG. 4, there is shown wafer 24 undergoing electron beamexposure step 44. A flood electron beam 52 impinges on the exposedsurfaces of wafer 24 and chemically transforms or modifies such exposedsurfaces to a certain depth. For feature 50, a top surface or region 54and sidewalls or side regions 56 are transformed into a shell 58.Similarly, for feature 51, a top surface or region 60 and sidewalls orside regions 62 are transformed into a shell 64. Hence, upon completionof step 44, feature 50 will comprise an untreated region 66 and shell58, untreated region 66 being encapsulated from underneath by layer 28and on all other sides or faces by shell 58. Similarly, feature 51 willcomprise an untreated region 68 and shell 64, untreated region 68 beingencapsulated from underneath by layer 28 and on all other sides or facesby shell 64.

[0033] Electron beam 52 is preferably emitted from an extended areaelectron source (not shown) and is a uniform collimated beam that isflood exposed over the entire wafer 24 at a normal angle of incidence.The extended area electron source is of the cold cathode type andgenerates electron beam 52 from the energetic impact of ions against asuitable metal. An example of an extended area electron source suitableto generate electron beam 52 is manufactured by Electron VisionCorporation.

[0034] The electron beam flood exposure conditions (e.g., beam current,dose, and accelerating voltage) are selected such that layer 30 will notmelt and flow, which will cause distortions in features 50, 51. Instead,conditions are selected to cause molecules of layer 30 which interactwith electron beam 52 to undergo a chemical change, i.e., cross-linking,to the extent that the functional groups of the polymer materialcomprising such molecules will become decomposed. Shells 58 and 64 arerepresentative of the decomposed regions of layer 30. The portions offeatures 50, 51 that electron beam 52 are unable to penetrate orbombard, i.e., untreated regions 66, 68, remain unaffected (i.e., thepolymer functional groups of untreated regions 66, 68 are notcross-linked to the point of complete decomposition).

[0035] The degree of decomposition that the functional groups of thepolymer material comprising layer 30 will undergo is a function of thedose of electron beam 52. In one embodiment, electron beam 52 isprovided at a beam current in the order of approximately 3 mA, a dose inthe range of approximately 500 to 4000 μC/cm², and preferably, atapproximately 2000 μC/cm², and an accelerating voltage of approximately3-5 keV. The conditions are selected to form shells 58, 64 configured tosuitably address the charging and outgassing problems associated withSEM analysis and inspection. Alternatively, when layer 30 comprisesother types of materials, the beam current and dosage of electron beam52 may be selected to cause desirable chemical changes such that thechanged portions of layer 30 will facilitate obtaining accurate CDmeasurements, as will be described in greater detail below.

[0036] The penetration depth of electron beam 52 into layer 30 is afunction of the energy of electron beam 52. The penetration depth alsodetermines the depth or thickness of each of shells 58, 64. In oneembodiment, the depth of shells 58, 64 can be selected as a function ofthe accelerating voltage of electron beam 52 and this relationship canbe approximately expressed as: $R_{g} = \frac{0.046V_{a}^{1.75}}{d}$

[0037] where R_(g) is the penetration depth in microns, V_(a) is theaccelerating voltage or energy in keV, and d is the density of thetarget material (e.g., layer 30) in g/cm³. Preferably, the acceleratingvoltage of electron beam 52 is provided at up to approximately 10 keV.More preferably, the accelerating voltage is in the range ofapproximately 3-5 keV.

[0038] In any case, the depth of shells 58, 64 is selected in accordancewith the performance or conditions associated with the SEM analysis andinspection carried out in step 46. In one embodiment, the depth ofshells 58, 64 is in the range of approximately 30 to 200 Å, and morepreferably, is up to 50 to 60 Å thick.

[0039] In step 46, SEM images of the patterned features on layer 30 aregenerated using an SEM analysis and inspection tool 100 (FIG. 5), toobtain CD measurements of such patterned features (e.g., to measure thelateral dimensions of features 50 and 51) before they are transferredonto underlying layers (e.g., layer 28) of wafer 24.

[0040] Tool 100 includes a chamber 102, an electron gun 104, an opticalassembly 106, detectors 108, a computer or analyzer 110, and a stage112. Although not shown, tool 100 may further include other components,such as, filters, analog-to-digital (A/D) converters, amplifiers,input/output devices, controllers, storage devices, etc.

[0041] In one embodiment, chamber 102 is maintained under vacuum at apressure of approximately 10⁻⁷ Torr. Electrons are emitted from electrongun 104 and configured into primary electrons 114 by optical assembly106. Optical assembly 106 may be one or more lens assemblies, and mayinclude lenses, filters, beam splitters, mirrors, etc., which generate afocused and collimated primary electrons 114. Primary electrons 114impinge on wafer 24, and in particular, on layer 30. Tool 100 preferablyimages a portion of wafer 24 at any given time and as such, wafer 24 maybe provided over stage 112 for translation. Alternatively, wafer 24 maybe stationary and tool 100 may move during step 46.

[0042] The interaction of primary electrons 114 with layer 30 causessecondary electrons (not shown) to be emitted from layer 30. Thesecondary electrons are collected by detectors 108 and electricalsignals representative thereto are communicated to computer 110 forprocessing and analysis. Although two detectors 108 are shown in FIG. 5,detectors 108 may comprise one or more detectors that are suitablypositioned relative to wafer 24 to receive the secondary electrons.Detectors 108 can be photomultiplier detectors. Computer 110 utilizesthe electrical signals from detectors 108 to generate SEM images of thesurface of wafer 24, i.e., the patterned features on layer 30. Such SEMimages are then inspected, either by a human operator or through anautomated process, to obtain CD measurements associated with thepatterned features on layer 30 (e.g., the lateral dimensions of features50 and 51) (step 48).

[0043] Ideally, primary electrons 114 should penetrate layer 30 up to acertain depth and only secondary electrons should be emitted from layer30. Otherwise, primary electrons 114 should have no other interactionwith or impact on wafer 24. In reality, SEM imaging causes, amongothers, a charge to build up in layer 30 and/or outgassing of volatilespecies from layer 30, resulting in SEM images with degraded imagecontrast and this, in turn, leading to erroneous CD measurements.Moreover, the heating and charging occurring in layer 30, if severeenough, can cause the patterned features to become permanentlydistorted. The electron beam treatment of step 44 advantageouslyminimizes or eliminates such problems.

[0044] The cross-linked regions (e.g., shells 58, 64) of layer 30 havedifferent structural or material properties relative to thenon-cross-linked regions (e.g., untreated regions 66, 68) of layer 30.Among others, the cross-linked regions are more dense, less porous, andare harder or stiffer than the none cross-linked regions. When the depthof shells 58, 64 is selected to be equal to or greater than thepenetration depth of primary electrons 114, the secondary electronsemitted from features 50, 51 are predominantly from shells 58, 64 (asopposed to untreated regions 66, 68). Because of the specific propertiesof shells 58, 64, they will not outgas volatile organic species uponinteraction with primary electrons 114. Moreover, since primaryelectrons 114 will have little or no interaction with untreated regions66, 68, outgassing of volatile organic species from untreated regions66, 68 is also minimized or eliminated.

[0045] When the depth of shells 58, 64 is selected to be less than thepenetration depth of primary electrons 114, the secondary electrons areemitted from both shells 58, 64 and untreated regions 66, 68 forfeatures 50, 51, respectively. Advantageously, volatile organic specieswhich would otherwise be outgassed from untreated regions 66, 68 intochamber 102 are trapped within layer 30 by shells 58, 64. Hence, shells58, 64 are configured with respect to the operating conditions of tool100 and the characteristics of the material comprising layer 30 (e.g.,an organic-based photoresist material) such that outgassing of volatileorganic species from layer 30 into chamber 102 is prevented by thetrapping or barrier capability of shells 58, 64. If volatile organicspecies were to escape layer 30, they would interact with and scatterprimary electrons 114, resulting in SEM images with poor contrast andpoor CD measurement accuracy. Examples of volatile organic speciesinclude isobutene, benzylic photoacid generator fragments, etc.

[0046] Shells 58, 64 also have different optical and electricalproperties relative to untreated regions 66, 68. The constituentmaterial elements comprising untreated regions 66, 68 (e.g., residualsolvent, photoresist additives, etc.) have different electricalproperties relative to each other which can impede smooth dissipation ofthe beam current associated with SEM imaging, leading to a charge buildup in features 50, 51. In contrast, the electrical and opticalproperties of shells 58, 64 are more uniform than those of untreatedregions 66, 68. Hence, not only are shells 58, 64 less likely to buildup a charge, their uniform or homogeneous electrical properties alsopromote smooth dissipation of any built-up charge. This results in SEMimages without degraded image contrast and also reduces distortions ordamage to features 50, 51, which may occur with significant chargingand/or heating problems.

[0047] It should be understood that SEM tool 100 as shown in FIG. 5 anddescribed herein are for illustration purposes only and are not meant tobe limiting. SEM tool 100 may be configured in a variety of other waysto perform a desired inspection of features patterned on layer 30 afterdevelopment but before pattern transfer to underlying layers.

[0048] Once SEM imaging data have been obtained via detectors 108, suchdata are analyzed and processed, as is well-known in the art, bycomputer 110 in step 48 to generate CD measurements that actuallyrepresent the lateral dimensions of features on layer 30.

[0049] In this manner, charging, heating, and/or outgassing problemsassociated with SEM inspection of features patterned on a photoresistlayer during IC fabrication can be significantly reduced or eveneliminated. An electron beam treatment of the photoresist layer tomodify its outer surfaces to a certain depth leads to the formation of ashell or barrier for each feature patterned on the photoresist layer.These shells prevent the outgassing of species which may scatter andinteract with the SEM's electron beam and provide a region for smoothlydissipating built-up charge or heat from the SEM's electron beam. Theresulting SEM images no longer suffer from image contrast problems andultimately the CD measurements obtained therefrom will be highlyaccurate. The patterned features are also less likely to becomepermanently distorted or damaged as a consequence of undergoing SEMinspection. In one embodiment, charging, heating, and/or outgassingproblems typically associated with SEM inspection of organic-basedphotoresist layer may be reduced by 95% or better.

[0050] It is understood that although the detailed drawings, specificexamples, and particular values describe the exemplary embodiments ofthe present invention, they are for purposes of illustration only. Theexemplary embodiments of the present invention are not limited to theprecise details and descriptions described herein. For example, althoughparticular materials or chemistries are described, other materials orchemistries can be utilized. Various modifications may be made in thedetails disclosed without departing from the spirit of the invention asdefined in the following claims.

What is claimed is:
 1. A method of inspecting a surface associated withmanufacture of an integrated circuit, the method comprising the stepsof: providing an electron beam to the surface; transforming at least aportion of the surface; and inspecting the surface using a scanningelectron microscope (SEM), wherein the transforming step occurs beforethe inspecting step.
 2. The method of claim 1, wherein the surfaceincludes at least one patterned feature having a top portion, sideportions, and a bottom portion, and the transforming step includeschemically changing the top portion and the side portions to form ashell that encapsulates the bottom portion.
 3. The method of claim 2,wherein the shell has a depth in the range of approximately 30 to 200 Å.4. The method of claim 2, wherein the surface is an organic-basedphotoresist layer.
 5. The method of claim 4, wherein the transformingstep includes decomposing polymer functional groups included in the topand the side portions.
 6. The method of claim 1, wherein the inspectingstep includes at least one of preventing volatile species from leavingthe surface and substantially dissipating a charge built up in thesurface.
 7. A patterned photoresist layer configured to facilitateaccurate critical dimension measurements of features thereon using ascanning electron microscope (SEM), the layer comprising: a treatedregion; and an untreated region, wherein the treated region comprises atop surface and side surfaces surrounding the untreated region, and thetreated region having at least one of a different electrical andmaterial property relative to the untreated region.
 8. The layer ofclaim 7, wherein the material comprising the patterned photoresist layeris an organic-based polymer.
 9. The layer of claim 7, wherein thetreated region is formed by flood exposing the patterned photoresistlayer to an electron beam.
 10. The layer of claim 9, wherein theelectron beam has a beam current of approximately 3 mA, a dose in therange of approximately 500-4000 μC/cm², and an accelerating voltage upto approximately 10 keV.
 11. The layer of claim 9, wherein the electronbeam has a dose of approximately 2000 μC/cm² and an accelerating voltagein the range of approximately 3-5 keV.
 12. The layer of claim 9, whereinthe electron beam cross-links and decomposes polymer functional groupsincluded in the material comprising the treated region.
 13. The layer ofclaim 7, wherein the treated region has a thickness of approximately 30to 200 Å.
 14. The layer of claim 7, wherein the treated region isconfigured to prevent outgassing species generated by the untreatedregion from coming into contact with the SEM.
 15. The layer of claim 7,wherein the treated region is configured to dissipate a charge generatedin the patterned photoresist layer in association with the use of theSEM.
 16. A process for reducing the build up of at least one of charge,heat, and volatile species in a photoresist layer during scanningelectron microscope (SEM) inspection, the process comprising: exposingthe photoresist layer to a flood electron beam, the photoresist layerincluding at least one patterned feature having a top surface, sidesurfaces, and an untreated portion; and forming a shell in thephotoresist layer in response to the flood electron beam, wherein theshell is comprised of the top surface and the side surfaces, and theshell reduces the build up of at least one of charge, heat, and volatilespecies associated with the at least one feature during SEM inspection.17. The process of claim 16, wherein the exposing step includes exposingthe flood electron beam having operating conditions of approximately 3mA, 500-4000 μC/cm², and up to 10 keV.
 18. The process of claim 16,wherein the shell surrounds the untreated portion and a thickness of theshell is approximately 30-200 Å.
 19. The process of claim 16, whereinthe forming step includes cross-linking the top surface and the sidesurfaces to form the shell.
 20. The process of claim 16, wherein theforming step includes decomposing the functional groups included in thetop surface and the side surfaces to form the shell.